Outer case for hot water unit, and hot water unit provided therewith

ABSTRACT

This outer case (C) for a hot water unit, configured using a metal plate ( 30   a ), is provided with a paint layer ( 30   b ) which is provided to cover the front surface and/or back surface of the metal plate ( 30   a ), an inkjet printing layer ( 4 ) which is laminated on the paint layer ( 30   b ) and which shows text, symbols, figures and/or patterns, and a clear layer ( 5 ) which covers the inkjet printing layer ( 4 ). By means of this configuration, the outer case (C) can be produced with high productivity and at a low cost, and with excellent design and resistance properties.

TECHNICAL FIELD

The present invention relates to a hot water unit in which a hot waterdevice for generating hot water or storing hot water, such as a hotwater supply device or a cogeneration system, is accommodated in anouter case, and the outer case.

BACKGROUND ART

As a specific example of a hot water unit configured as a hot watersupply device, there is an example in which a hot water device, whichheats water using combustion gas generated by a burner, is accommodatedin an outer case (for example, see Patent Literatures 1 to 3). The outercase for the hot water unit is generally manufactured by pressing acolored steel plate having a front surface of a single color.

In such a hot water unit, for example, in addition to displaying text orsymbols representing a manufacturer name, a type, an ability or the likeof the hot water unit on the outer case, in some cases, a wide range ofthe surface of the outer case needs to be covered with a color differentfrom a ground color of the surface of the colored steel plate. In thiscase, in the related art, after forming component parts of the outercase (an outer case main body and a cover body) by press molding, thecomponent parts are painted by a spray method.

However, in the above-mentioned related art, there is the following roomfor improvement.

When the spray-type painting means of the related art is used, maskingof an unpainted portion and color matching of the paint are troublesome.In addition, work of spraying paint using a spray gun (an air gun) isalso troublesome and requires skill. Therefore, workability andproductivity are poor. Furthermore, since the paint is sprayed onto themasking portion, much paint is wasted. Therefore, the manufacturing costof the outer case and the manufacturing cost of the hot water unitincrease. As the pattern to be painted becomes more complicated and thenumber of colors increases, such defects become remarkable. According tosome spray methods, it is also difficult to express detailed patterns.

In the related art, a transfer type coating means has also beenappropriately adopted. However, according to the coating means of thistransfer method, a transfer plate is required, which leads to a highcost. Moreover, it is not suitable for painting a large area.

On the other hand, the paint applied to the outer case is easily damagedby influences of wind and rain or sunlight including ultraviolet rays,and contamination and fading are likely to occur.

CITATION LIST Patent Literature

-   [Patent Literature 1]

Japanese Patent Laid-Open No. 2012-32029

-   [Patent Literature 2]

Japanese Patent Laid-Open No. H11-294867

-   [Patent Literature 3]

Japanese Patent Laid-Open No. 2014-40950

SUMMARY OF INVENTION Technical Problem

An objective of the present invention is to provide an outer case for ahot water unit capable of appropriately solving the above-mentionedproblems, and a hot water unit provided with the outer case.

Solution to Problem

In order to solve the above problems, the following technical measuresare taken in the present invention.

An outer case for a hot water unit provided in a first aspect of thepresent invention is an outer case for a hot water unit configured usinga metal plate, which includes a paint layer provided to cover at leastone of a front surface and a back surface of the metal plate; an inkjetprinting layer which is laminated on the paint layer and represents atleast one of text, symbols, figures or a pattern; and a clear layerwhich covers the inkjet printing layer.

Preferably, the clear layer contains an ultraviolet absorber.

Preferably, the outer case includes an outer case main body having anopening on at least one surface, and a cover body attached to the outercase main body to close the opening, and at least one of the outer casemain body and the cover body has a configuration in which the paintlayer, the inkjet printing layer, and the clear layer are provided onthe outer surface of the metal plate.

Preferably, the metal plate is provided with a drawing portion, and in aportion of the drawing portion in which a plate thickness of the metalplate is thinner than that of another portion, a thickness of the inkjetprinting layer is also thinner than that of the other portion.

Preferably, the metal plate is provided with a burring hole into which aburring portion protrudes on the peripheral portion, a first inkjetprinting layer provided in a peripheral portion of the burring hole anda second inkjet printing layer provided in the burring portion to beconnected to the first inkjet printing layer are included as the inkjetprinting layer, and the first and second inkjet printing layers arecovered serially by the clear layer.

Preferably, at least some component parts of the outer case are pressedproducts, and a positioning mark for pressing of the component parts isprovided as the inkjet printing layer.

A hot water unit provided in a second aspect of the present inventionincludes the outer case for the hot water unit provided in the firstaspect of the present invention.

Other features and advantages of the present invention will become moreapparent from the following description of embodiments of the inventionwith reference to the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a side view representing an example of a hot water unitaccording to the present invention, and FIG. 1B is an explodedperspective view of an outer case (a state in which an internal hotwater device is omitted) of the hot water unit shown in FIG. 1A.

FIG. 2A is a side view of a state in which a clear layer is omitted inFIG. 1A, and FIG. 2B is an exploded perspective view of a state in whichthe clear layer is omitted in FIG. 1B.

FIG. 3A is a front view of a state in which the clear layer of the coverbody of the outer case shown in FIGS. 1A and 1B is omitted, and FIG. 3Bis a front view of a state in which an inkjet printing layer of thecover body is omitted.

FIG. 4A is a cross-sectional view along a line IVA-IVA of FIG. 3A, FIG.4B is a cross-sectional view of a main part along a line IVB-IVB of FIG.3A, FIG. 4C is a cross-sectional view of a main part along a lineIVC-IVC of FIG. 3A, and FIG. 4D is a front sectional view of a portionindicated by reference numeral IVD of FIG. 3A.

FIG. 5 is a rear view of the cover body shown in FIGS. 1A to 3A.

FIGS. 6A to 6G are explanatory views representing an example of themanufacturing process of the cover body shown in FIGS. 1A to 3A.

FIG. 7 is a cross-sectional view of a main part which shows an exampleof a colored steel plate used for manufacturing the cover body shown inFIGS. 1A to 3A.

FIG. 8A is a perspective view representing an example of a schematicconfiguration of a printer used for inkjet printing, and FIG. 8B is aview taken along an arrow VIIIB of FIG. 8A, representing a schematicstructure of a print head of the printer shown in FIG. 8A.

FIG. 9 is cross-sectional view of the main part which shows an exampleof the working process for obtaining a structure of FIG. 4C.

DESCRIPTION OF EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will bespecifically described with reference to the drawings.

A hot water unit U shown in FIGS. 1A to 2B corresponds to a hot watersupply device and includes an outer case C, and a hot water device 1 forgenerating hot water is accommodated inside the outer case C. The hotwater device 1 is equipped with a heat exchanger 10 through which hotwater flows, a burner 11 for heating the hot water in the heat exchanger10, and a fan 12 for supplying combustion air to the burner 11.

The outer case C is equipped with a substantially rectangularparallelepiped outer case main body 2 having an opening 20 on a frontsurface, and a cover body 3 (a front cover body) that closes the opening20. The cover body 3 is detachably attached to the front surface portionof the outer case main body 2 by utilizing, for example, a screw body 9such as a screw, and screw body insertion holes 31 and 21 through whichthe screw body 9 is inserted.

In the present embodiment, the cover body 3 is provided with an inkjetprinting layer 4 (a portion having a halftone dot pattern or a wavy linepattern in the drawing) and a clear layer 5. The outer case main body 2is not provided with these. Therefore, the configuration of the coverbody 3 will be described below in detail, and the description of theouter case main body 2 will be omitted. However, as will be describedbelow, an inkjet printing layer or a clear layer can be provided on theouter case main body 2.

The cover body 3 is a configuration in which an inkjet printing layer 4(4 a to 4 g) (see also FIGS. 3A and 5), and the clear layer 5 areprovided on the colored steel plate 30 after press-molding (a metalplate provided with a paint layer).

The cover body 3 has a panel shape having a substantially rectangularshape in a front view, and is equipped with an outer peripheral flangeportion 32, and a bulging portion 33 which is surrounded by the outerperipheral flange portion 32 and bulges to the front of the outerperipheral flange portion 32 (a front side of the outer case C). Theouter peripheral flange portion 32 is a portion for abutting on thesubstantially rectangular frame-shaped flange portion 22 provided on thefront surface portion of the outer case main body 2, and as shown inFIG. 4A, a folded-back portion 32 a formed by hemming process iscontinuously provided on the outer edge portion thereof.

The bulging portion 33 of the cover body 3 occupies most of the coverbody 3, and the bulging portion 33 is provided with an air supply port34 and an exhaust port 35 (see also FIGS. 3A and 3B). The air supplyport 34 is a portion that allows outside air to flow into the outer caseC. The exhaust port 35 is a portion for discharging the exhaust gasafter heat recovery by the heat exchanger 10 to the outside of the outercase C. As shown in FIG. 4C, the exhaust port 35 is formed as a burringhole on the peripheral edge portion of which a tubular burring portion35 a is continuously provided.

The inkjet printing layer 4 is a coating film layer provided byutilizing an inkjet printer 8 as will be described below. As the ink forinkjet printing, a water-based pigment ink or a solvent-based pigmentink can be used. Preferably, the ink contains an ultraviolet curableresin and a thermosetting resin.

Inkjet printing layers 4 a to 4 d representing a predetermined patternD1 such as a penguin, and an inkjet printing layer 4 e representing textD2 (“AABBCC” as an example in the drawing) indicating, for example, amaker, a model or a trademark of the hot water unit U provided on thesurface of the cover body 3 are provided as the inkjet printing layer 4.An inkjet printing layer 4 f representing a positioning mark D3 forpressing, which will be described later, is provided at the four cornersof the cover body 3. The positioning mark D3 is shown in the shape of“+” in the drawing, but is not limited thereto. Further, the positioningmark D3 may be configured to be provided on the back surface of thecover body 3 instead of or in addition to the front surface of the coverbody 3.

As shown in FIG. 5, an inkjet printing layer 4 g representing anelectrical wiring diagram D4 of the hot water device 1 is furtherprovided on the back surface of the cover body 3. Instead of or inaddition to the electrical wiring diagram D4, it is also possible toprovide a configuration representing a piping diagram of the hot waterdevice 1. Although this is not illustrated or described, it is alsopossible to provide a configuration in which an inkjet printing layerrepresenting a specification description, notes, or the like of the hotwater unit U is further provided on the back surface of the cover body3, in addition to the electrical wiring diagram D4 and the pipingdiagram.

As shown in FIG. 7, the colored steel plate 30 is a raw material of thecover body 3 and has a multi-layer structure with a plated steel sheet30 a (metal plate), a whitish (or white) coating layer 30 b on a frontside laminated on the surface of the plated steel sheet 30 a, and acoating layer 30 c on a back side as a service coat laminated on theback surface of the plated steel sheet 30 a. The inkjet printing layers4 a to 4 e have colors different from those of the whitish front sidecoating layer 30 b, and represent a design D1 such as the appearance ofthe penguin and text D2. The white portion of FIG. 3A is a portion ofthe front side coating layer 30 b of the colored steel plate 30 that hasnot been subjected to inkjet printing.

The entire region of the inkjet printing layer 4 a is basically formedin the same color and to the same thickness. However, as shown in FIG.4D, a thickness ta of a corner portion 33 a′ of a peripheral wallportion 33 a (a wall portion rising forward from the outer peripheralflange portion 32) of the bulging portion 33 is thinner than a thicknesstb of another portion of the peripheral wall portion 33 a, and athickness of the portion other than the peripheral wall portion 33 a.The bulging portion 33 is formed by the drawing process, and theperipheral wall portion 33 a thereof corresponds to the drawing portion.According to the drawing process, an amount of extension of the colorsteel plate 30 of the corner portion 33 a′ of the peripheral wallportion 33 a is the largest (the corner portion 33 a′ corresponds to a‘portion in which the plate thickness of the metal plate is thinner thanother portions, in the drawing portion’). If the thickness ta of theinkjet printing layer 4 a in the corner portion 33 a′ decreasesaccordingly, it is possible to obtain the effect of preventing theinkjet printing layer 4 a from peeling, as will be described later. Whenthe amount of drawing (the amount of extension) of the peripheral wallportion 33 a is increased to increase the amount of bulging of thebulging portion 33, it is possible to provide a configuration in whichthe thickness tb of the portion of the peripheral wall portion 33 aother than the corner portion 33 a′ is thinner than the thickness ofother portions of the inkjet printing layer 4 a.

The inkjet printing layer 4 b is provided in the peripheral portion ofthe exhaust port 35. As described with reference to FIG. 4C, the exhaustport 35 is formed as a burring hole having a burring portion 35 a. Incontrast, a part of the inkjet printing layer 4 b is also provided onthe inner surface of the burring portion 35 a. As a result, theperipheral portion of the exhaust port 35 and the inner surface of theburring portion 35 a can be aligned in the same color or pattern, andthe appearance of the exhaust port 35 and its peripheral portion can beimproved.

The inkjet printing layer 4 e is provided on the front surface of a steppressing portion 36 (see also FIGS. 3B and 4B) that three-dimensionallyrepresents the text D2. More specifically, the step pressing portion 36is a portion in which the text D2 is three-dimensionally formed bypartially extruding a part of the colored steel plate 30 by pressing,and the inkjet printing layer 4 e is provided on the front surfaceportion of such a step pressing portion 36. Although the step pressingportion 36 includes a front convex form in which a part of the coloredsteel plate 30 is extruded to the front side of the cover body 3, and afront concave form in which a part of the colored steel plate 30 isextruded to the rear side of the cover body 3, it does not matter whichone is adopted.

The clear layer 5 is formed over substantially the entire region of thefront surface part of the cover body 3 to cover the inkjet printinglayer 4. As shown in FIG. 4B, the clear layer 5 is also formed in arecess in a region forming the text D2. Further, as shown in FIG. 4C,the clear layer 5 is also provided on the inner surface of the burringportion 35 a, and serially covers the inkjet printing layer 4 of theinner surface of the burring portion 35 a, the inkjet printing layer 4around the exhaust port 35 (burring hole) or the like. Since the backsurface of the cover body 3 is not directly exposed to wind, rain orsunlight, the clear layer 5 is not provided. However, it is possible toprovide a configuration in which the clear layer 5 is also provided onthe back surface of the cover body 3 to protect the inkjet printinglayer 4 g. In this case, instead of providing the clear layer 5 on theentire back surface, it is possible to provide a configuration in whichthe clear layer 5 is provided only in a region in which the inkjetprinting layer 4 g is provided. The clear layer 5 is made of a resinpaint that does not contain a pigment, but contains an ultravioletabsorber. Further, the clear layer 5 is made of a thermosetting resin oran ultraviolet curable resin.

The aforementioned cover body 3 can be manufactured via the followingsteps.

First, as shown in FIG. 6A, a flat plate-shaped colored steel plate 30described with reference to FIG. 7 is prepared as a raw material for thecover body 3. Next, the inkjet printing layer 4 is provided as shown inFIG. 6B, by performing inkjet printing on the colored steel plate 30(strictly speaking, on the paint layers 30 b and 30 c of the coloredsteel plate 30). The inkjet printing is performed using, for example, aninkjet printer 8 as shown in FIG. 8A. In the inkjet printer 8, the printhead 80 is movable in the x and y directions orthogonal to each other onthe upper side of a mounting table 81 on which the colored steel plate30 is mounted and supported.

As shown in FIG. 8B, the print head 80 includes a plurality of inkjetnozzles 82 that atomize an inkjet paint of a predetermined color andspray it toward the colored steel plate 30. This point is the same asconventional knowledge, but a pair of ultraviolet light sources 83 (83a, 83 b) are further provided in the vicinity of the inkjet nozzle 82.

For example, when inkjet printing is performed while the print head 80is moved in the x1 direction of FIG. 8B as a main scanning direction, anultraviolet light source 83 a on the rear side in the main scanningdirection is made to emit light, and ultraviolet rays are radiated tothe region immediately after the inkjet printing. Since the inkjetprinting layer 4 contains an ultraviolet curable resin, the inkjetprinting layer 4 can be rapidly cured (cured to the extent that bleedingdoes not occur, which will be described later) by irradiation of theultraviolet rays.

Therefore, it is possible to prevent the uncured inkjet printing layers4 having different colors from being mixed with each other and causingbleeding. When the inkjet printing is carried out in a directionopposite to the x1 direction described above, the same effect asdescribed above can be obtained by causing the ultraviolet light source83 b to emit light instead of the ultraviolet light source 83 a.

When the inkjet printing layer 4 a is provided, the thickness to of thecolored steel plate 30 at a planned portion which is the corner portion33 a′ of the peripheral wall portion 33 a shown in FIG. 4D is set to bethinner than the thickness tb of other portions.

After the above-mentioned inkjet printing on both the front and backsurfaces of the colored steel plate 30 is completed, as shown in FIG.6C, while heating the color steel sheet 30 and drying the inkjetprinting layer 4, the thermosetting resin contained in the inkjetprinting layer 4 is cured. The heating is performed using, for example,a heating furnace. By such a process, the strength of the inkjetprinting layer 4 can be increased, and in addition, the durabilityagainst the pressing to be performed thereafter can also be improved.

Next, the colored steel plate 30 is subjected to drawing process as apressing to form an outer peripheral flange portion 32 and a bulgingportion 33 as shown in FIG. 6D. After that, as shown in FIG. 6E, thepressing step for forming the air supply port 34, the exhaust port 35,the step pressing portion 36, and the like, the trimming process forremoving an excess portion of the outer peripheral flange portion 32, asubsequent hemming process and the like are performed. As a result, thecover body 3 described above can be manufactured. In the above workingprocess, the colored steel plate 30 can be accurately positioned withreference to the positioning mark D3. The work of forming the exhaustport 35 is performed by utilizing a punch 7 a and a die 7 b, forexample, as shown in FIG. 9. In contrast, in addition to the peripheralportion of the planned formation location of the exhaust port 35, theinkjet printing layer 4 b is also provided serially at the formationtarget portion of the exhaust port 35. Therefore, as shown in FIG. 4C,it is possible to appropriately realize a configuration in which theinkjet printing layer 4 b is provided serially from the peripheralportion of the exhaust port 35 to the burring portion 35 a.

After the outer shape of the cover body 3 is finished as describedabove, as shown in FIG. 6F, the cover body 3 is subjected to clearcoating to form the clear layer 5 over substantially the entire regionof the front surface of the cover body 3. The clear paint is mainly madeof a thermosetting resin (or an ultraviolet curable resin) containing anultraviolet absorber. The clear coating is, for example, a spray coatingin which a clear paint is sprayed from a spray nozzle 88. After theclear coating is completed, the clear layer 5 is heated, dried and curedas shown in FIG. 6G The heating is, for example, heating using a heatinglamp. Alternatively, when the clear layer 5 is made of an ultravioletcurable resin, it is cured by ultraviolet irradiation.

Next, the operations of the outer case C provided with the cover body 3and the hot water unit U will be described.

First, since the design D1 such as the penguin is displayed on the frontsurface portion of the cover body 3, for example, the hot water unit Ucan have excellent design properties, as compared with a case in whichthe surface of the cover body 3 has a single color or no pattern. Sincethe inner surface of the burring portion 35 a of the exhaust port 35 iscontinuously painted on the peripheral portion of the exhaust port 35,the appearance is also better than in a case in which the inside of theburring portion 35 a is colored differently from the peripheral portionof the burring portion 35 a. Further, in the corner portion 33 a′ of theperipheral wall portion 33 a, a part of the colored steel plate 30greatly extends in the drawing process. However, since the thickness toof the inkjet printing layer 4 in this portion is thinner than thethickness tb of the other portion, it is also possible to prevent theproblem of the inkjet printing layer 4 being easily peeled off in theabove-mentioned drawing process.

Since the electrical wiring diagram D4 or the piping diagram isrepresented by the inkjet printing layer 4 g on the back surface of thecover body 3, it is convenient for maintenance work and the like. Forexample, when the means such as a sheet with a printed electrical wiringdiagram is stuck to the back surface of the cover body 3, the sheet maybe damaged or peeled off of the cover body 3 and lost. In contrast,according to the present embodiment, there is no such risk.

Since the coating film layer representing the design D1, the text D2,the positioning mark D3, the electrical wiring diagram D4, and the likeof the cover body 3 is all included in the inkjet printing layer 4, itcan be easily provided using the inkjet printer 8 as described above.

For example, unlike painting by the spray method, a masking process andcolor matching of paint are not required, and skill is not required.Therefore, it is possible to improve workability and productivity. Inaddition, it is easy to change the design of the design D1 and the like,and it is suitable for small-quantity and large-variety production.Further, according to the inkjet printing, there is little to no wasteof ink paint, and it is economical. Since the base material of theinkjet printing layer 4 is the paint layers 30 b and 30 c of the coloredsteel plate 3, it is also possible to improve the appearance, weatherresistance or the like of the location in which the inkjet printinglayer 4 is not provided.

The clear layer 5 enables various expressions such as glossy and matte,and further improves the design of the outer case C. Further, since theclear layer 5 covers and protects the inkjet printing layer 4 on thefront surface portion of the cover body 3, the weather resistance of theinkjet printing layer 4 is enhanced and the stain resistance isexcellent. In particular, since the clear layer 5 contains anultraviolet absorber, the color of the inkjet printing layer 4 does notfade due to the ultraviolet rays of sunlight. Further, the clear layer 5also has an effect of suppressing the peeling of the inkjet printinglayer 4. Because the clear layer 5 is provided in substantially theentire region of the front surface portion of the cover body 3, theaforementioned effect is more excellent.

The present invention is not limited to the content of theabove-described embodiment. The specific configuration of the outer casefor hot water unit according to the present invention and each part ofthe hot water unit can be variously redesigned within the scope intendedby the present invention.

Although the above-described embodiment is an example in which only thecover body 3 is subjected to inkjet printing or clear coating, in thepresent invention, it is possible to provide a configuration in whichthe outer case main body 2 is also subjected to inkjet printing or clearcoating, instead of or in addition to this. The outer case main body maybe subjected to only the clear coating and not subjected to inkjetprinting. The specific content such as text and patterns represented bythe inkjet printing layer of the present invention is not limited, andat least one of text, symbols, figures, and patterns may be represented.The clear layer may be colored and transparent instead of colorless andtransparent.

The hot water unit according to the present invention can also beconfigured as a hot water storage tank unit or the like in which a hotwater device for storing hot water, such as a hot water storage tank, isaccommodated in the outer case, instead of a configuration in which ahot water device for generating hot water such as a hot water supplydevice is accommodated in the outer case. Therefore, the outer case isnot limited to a combination of the front opening-shaped outer case mainbody and the cover body that closes the front opening.

Although a flat metal plate is used as the material of the outer case,it is possible to use a material different from the commerciallyavailable colored steel plate as the metal plate.

1. An outer case for a hot water unit configured using a metal plate,the outer case comprising: a paint layer provided to cover at least oneof a front surface and a back surface of the metal plate; an inkjetprinting layer which is laminated on the paint layer and represents atleast one of text, symbols, figures or a pattern; and a clear layerwhich covers the inkjet printing layer.
 2. The outer case for a hotwater unit according to claim 1, wherein the clear layer contains anultraviolet absorber.
 3. The outer case for a hot water unit accordingto claim 1, wherein the outer case includes an outer case main bodyhaving an opening on at least one surface, and a cover body attached tothe outer case main body to close the opening, and at least one of theouter case main body and the cover body has a configuration in which thepaint layer, the inkjet printing layer, and the clear layer are providedon an outer surface of the metal plate.
 4. The outer case for a hotwater unit according to claim 1, wherein the metal plate is providedwith a drawing portion, and in a portion of the drawing portion in whicha plate thickness of the metal plate is thinner than that of anotherportion, a thickness of the inkjet printing layer is also thinner thanthat of the other portion.
 5. The outer case for a hot water unitaccording to claim 1, wherein the metal plate is provided with a burringhole into which a burring portion protrudes on a peripheral portion, afirst inkjet printing layer provided in a peripheral portion of theburring hole and a second inkjet printing layer provided in the burringportion to be connected to the first inkjet printing layer are includedas the inkjet printing layer, and the first inkjet printing layer andthe second inkjet printing layer are covered serially by the clearlayer.
 6. The outer case for a hot water unit according to claim 1,wherein at least some component parts of the outer case are pressedproducts, and a positioning mark for pressing of the component parts isprovided as the inkjet printing layer.
 7. A hot water unit comprisingthe outer case for a hot water unit according to claim 1.